What Happens When Scientists Revive Activity in Animal Organs After Death?

In 2022, a team at Yale connected pigs that had been dead for an hour to a machine and watched their hearts begin to contract. The animals did not wake up, and the researchers were emphatic that they were not alive. But cells across their bodies had done something cells were not thought able to do.

What did the researchers actually do?

Two experiments, three years apart, both published in Nature. In 2019, a team led by neuroscientist Nenad Sestan took brains from pigs slaughtered for food and, four hours after death, connected them to a system they called BrainEx, which pumped a warm blood substitute through the vessels. Some cellular function returned: cells consumed oxygen and glucose, and tissue structure was preserved. There was no coordinated electrical activity of the kind associated with consciousness.

In 2022 the team, including David Andrijevic and Zvonimir Vrselja, adapted the approach to whole bodies. Anesthetized pigs were put into cardiac arrest and left for an hour. Then they were connected to OrganEx, a device like a heart-lung machine that circulated a solution of the animals’ own blood mixed with 13 compounds, including anticoagulants, anti-inflammatory drugs, and agents to prevent cell death, according to Nature’s report. After six hours, hearts were contracting, though not fully beating; cells in the heart, liver, and kidneys showed metabolism and switched on genes involved in repair; and under a microscope it was difficult to tell a treated organ from a healthy one, Vrselja told the Washington Post. Pigs on a standard heart-lung machine, by comparison, showed widespread cell death.

Were the pigs alive?

No. None showed coordinated brain activity indicating consciousness, according to Scientific American, and the Yale team said they did not view the work as redefining death. Some electrical activity was detected in the brain, but nowhere near what consciousness would require, IEEE Spectrum reported. The researchers noted the brain might have been quiet partly because the solution was cooler than body temperature. The hearts contracted but did not pump effectively, and the animals remained under anesthesia throughout.

What does the work show?

Mainly that cells die more slowly than medicine assumed. “The main takeaway was that things don’t die as quickly as we assumed they do,” Vrselja said of the 2019 study. When blood flow stops, cells begin a cascade toward death, but the cascade can apparently be interrupted for longer than an hour. Vrselja and Sestan expected the whole-body result because the brain is the organ most vulnerable to loss of blood, so if brain cells could be rescued, other organs should be too.

What could it be used for?

Transplants are the first hope. Organs from donors whose hearts have stopped deteriorate quickly, and a method that preserves or restores them after an hour could expand the supply, according to Scientific American. The team also hopes the approach might limit damage to a heart after a heart attack or a brain after a stroke, the New York Times reported. Yale has filed for a patent. All of this is years from human use, and the researchers themselves said the results were not yet clinically relevant.

Why has it raised questions about death?

Because the pigs met the standard definition of death and their cells were brought back to activity. Brandan Parent, a transplant ethicist at New York University, told the Times that by the accepted medical and legal definition the pigs were dead. Arthur Caplan of NYU told Nature that there is little consensus on when cardiac death occurs and that the legal definition of death will have to keep adapting as medicine advances. Paul Root Wolpe of Emory said the work raises the question of redefining what death is.

The sharpest concern is about organ donation after circulatory death, where organs are recovered after the heart has stopped and a short waiting period has passed. Parent wrote in Nature that a better ability to resuscitate people could make it harder to justify recovering organs after the heart or lungs stop. If a technique could restore organ function an hour later, when exactly is a person beyond saving? See brain death versus coma and organ and tissue donation after death.

What should a reader take from this?

Three things. Death at the cellular level is a process, not an instant, and medicine’s line is drawn by practical judgment, not by a switch in the body. The studies were about cells and organs, not about reviving a person, and no consciousness returned. And the questions they raise, about transplant timing and the definition of death, are already live for ethicists and doctors, which is why the research drew such attention. For a related and older puzzle, see the Lazarus phenomenon.

This is general educational information, not medical advice. Research in this area moves quickly and this page reflects sources available at the date shown; check the date and the sources before relying on a specific claim.